1. Field of the Invention
The present invention relates generally to multiple pane window units, and more particularly, to multiple pane window units having a non-metal, flexible, spacing and sealing assembly.
2. Discussion of the Technological Environment
Multiple pane window units generally comprise a pair of glass sheets maintained in spaced-apart relationship to each other by a spacing and sealing assembly extending around the marginal periphery of the inner, facing surfaces of the sheets, to define a substantially hermetically sealed, insulating air space between the sheets. The spacing and sealing assembly generally comprises an inner spacer-dehydrator element extending around the marginal periphery of the inside facing surfaces of the glass sheets and an outer sealing element extending around the outside periphery of the inner spacer-dehydrator element.
In one typical form of multiple pane window construction, the inner spacer-dehydrator element comprises a hollow metal spacer element generally adhered by a mastic composition to the marginal periphery of the inside, facing surfaces of the sheets, to provide a primary hermetic seal. The metal spacer element is generally tubular in shape and filled with a desiccant material, which is put in communication with the insulating air space to absorb moisture therefrom to enhance the performance and durability of the unit. The outer sealing element generally comprises a resilient, moisture-resistant strip placed around the marginal periphery of the glass sheets and the outer periphery of the inner spacer-dehydrator element to provide a secondary hermetic seal. A drawback of multiple pane window units having a metal spacer element is the cost of fabricating the metal spacer element.
U.S. Pat. No. 3,791,910, issued to the present Inventor, G. H. Bowser, and assigned to the assignee of the instant invention, teaches a multiple glazed unit having resilient inner and outer spacing and sealing assembly elements. The inner spacer-dehydrator element comprises a desiccant material dispersed throughout a moisture vapor transmittable matrix material, such as a material selected from the family of thermoplastic elastomers comprising block copolymers of styrene and butadiene. The matrix material is adhered to the marginal periphery of the inner, facing surfaces of the glass sheets by means of a continuous bead or ribbon of an adhesive moisture-resistant, mastic composition which forms an adhesive structural bond to maintain the sheets about the spacer at a predetermined spacing. The outer sealing element includes a continuous bead or ribbon of an adhesive, moisture-resistant material. A drawback with this type of multiple glazed unit is that the spacer-dehydrator element is not self-adhering to the sheets, thereby increasing the complexity of the fabrication/manufacture of the unit.
U.S. Pat. Nos. 4,226,063 and 4,205,104 issued to Chenel teach a multiple pane window unit having a spacing and sealing assembly comprised of an inner filament made of a first plastic material such as desiccant containing polyisobutylene and an outer mastic layer consisting of a second organic material such as a silicone or polysulfide elastomer. The outer mastic layer forms an adhesive structural bond with the glass sheets and provides for the mechanical stability of the window, while simultaneously ensuring water tightness of the unit. A disadvantage of the Chenel window units is that the inner filament does not contribute to the mechanical stability of the unit. A disadvantage of the Chenel unit is that the inner filamentary seal is has very low moisture vapor permeability which limits migration of moisture from the airspace into the polyisobutylene material of the inner filamentary seal. This property is undesirable because moisture is prevented from being removed readily from the insulating airspace to prevent hazing or fogging of the unit, and eventually, buildup of moisture on the inner glass sheet surfaces, which may cause staining and scumming thereof, will occur. It would be preferable to have desiccant material dispersed in a moisture vapor transmittable matrix to improve communication of the desiccant with the airspace, to thereby increase the rate of moisture vapor removal from the airspace. The Chenel patents further teach an inner filamentary seal comprised of two or more juxtaposed layers, the concentration of desiccant material dispersed through each layer increasing progressively from the outside to the inside of the unit, to purportedly improve the rate of moisture removal from the airspace. This design unduly complexifies the fabrication of the unit.
U.S. Pat. No. 4,198,254 issued to Laroche teaches a hollow panel prepared by uniting vitreous sheets by means of a spacer made of synthetic polymeric material. The synthetic polymeric material preferably comprises a hardenable viscoelastic ribbon having a tensile strength of at least 4 kg./cm.sup.2, an elongation at break in excess of 50%, and a water permeability of less than 0.2 g. of water per m..sup.2 of surface per 24 hours per mm. of material thickness per cm. of Hg pressure. Due to the impermeability of the spacer material, it is necessary, in order to obtain an appropriate rate of moisture removal from the panel airspace, to employ a separate desiccant-containing strip in communication with the airspace. A limitation of this teaching is that the mechanical stability of the unit depends entirely upon the outer spacer element.
It would therefore be desirable to have a multiple pane unit which eliminates the disadvantages and limitations of the prior art units.